1. Field of the Invention
The invention relates to a continuous-casting mold for casting thin slabs, the mold having an oblong inner cross-sectional area and cooled mold walls. The melt is poured in through at least one delivery nozzle which dips into the melt. The invention further relates to a process for continuously casting thin slabs.
2. Discussion of the Prior Art
In the continuous casting of strands having an oblong cross section, it is known to form the inner cross-sectional area of the continuous-casting mold so that a strand section as close as possible to the desired final dimensions is produced by the continuous-casting mold. In this case, especially those section beams having an H-shaped cross section and also those having a cross section in which the cross-sectional ends have thickenings (dog bone-shaped cross section), the problem regularly arises that the ends, which are widened and/or thickened relative to the web width, of the section beam frequently show cracks and stresses and/or undesired crystal structures are cast close to the final dimensions. In the case of section strands not cast close to the final dimensions, however, technically involved and cost-intensive rolling processes are required after casting in order to obtain the desired final dimensions.
DE 2,034,762 A1 has disclosed a process and apparatus for producing a thin strip, in which the strip has a thickening which extends in its longitudinal direction and which still has a liquid core. This thickening is then forced back underneath the mold by pressure rollers.
U.S. Pat. No. 5,082,746 discloses specially dimensioned section strands which must not exceed predetermined cross-sectional parameters arid which have a predetermined homogeneous crystal structure, so that the desired cross-sectional profile can then be obtained with the minimum of rolling work. Such section strands can, as experience shows, be cast using one or more delivery nozzles for pouring in the melt. In this case, it has been found that merely the restriction of the cross-sectional parameters and the setting of a desired crystal structure are not sufficient to produce section strands close to the final dimensions without cracks, and with a homogeneous crystal structure over the entire cross section. It is also insufficient, in the case of a strand section with flanks molded onto the ends, to select the web width to be equal to the flank width, as is explicitly suggested in U.S. Pat. No. 5,082,746. In fact, section strands produced specifically under these conditions regularly show cracks and, particularly in the zone of the flanks, a less favorable crystal structure than that of the web, which indicates that uniform casting conditions in each cross-sectional zone during casting with the use of immersed delivery nozzles cannot simply be achieved by adhering to limiting values of the above-mentioned cross-sectional parameters.